Currently, the pesticidal treatment of stored foodstuffs, chambers, structures and works of art is essentially carried out according to two techniques:                fumigation, using in particular methyl bromide (MB) and phosphine (PH3) which act in the gaseous state on the respiratory chain of the target organisms,        so-called “contact” treatments using, for example, organophosphorus insecticides, in particular dichlorvos, which act in the condensed state directly on the target organisms.        
Methyl bromide (MB) exhibits in the gaseous state excellent nematicidal, fungicidal, insecticidal and bactericidal properties. Unfortunately, this compound contributes to depletion of the ozone layer and, in accordance with the Montreal Accord (1992), by 2005 it should no longer be used in industrialized countries. Phosphine (PH3) exhibits major disadvantages such as its toxicity, the duration of the treatments and the corrosion of equipment in which this compound is used (Pest Control (1999) Vol. 67(1), p. 46).
Moreover, organophosphorus compounds have an activity spectrum reduced to their insecticidal action and generate toxic residues. In addition, since they only act through contact directly with the target organisms, they cannot reach the so-called hidden forms of these organisms; accordingly, the eggs and larvae of the insects present inside the grains of wheat and maize are not killed by the insecticide. This type of treatment is markedly less effective.
There is therefore an urgent need to provide users with alternative solutions which are effective and which are as environmentally friendly as possible. Examples of fumigant products under development for these applications are known and are described in various articles, in particular in World Grain, February 2001, p. 28-30 and Crop Prot. (2000) 19 (8-10), p. 577-582); but the solutions envisaged also exhibit major disadvantages such as their high cost (methyl iodide), their low availability (carbon oxysulphide) or their toxicity (sulphuryl fluoride).
Another family of compounds, the sulphur-containing products derived from substances produced by certain plants, for example the Alliums, is also known for its pesticidal and repellent activity and has already been the subject of numerous publications (Ecologie (1994) 25(2), p 93-101, Ed. Tec. and Doc., Biopesticides d'origine végétale (2002) p 77-95, Insect Sci. Applic. (1989) 10(1), p. 49-54, Pestic. Sci. (1999), Vol. 55, p. 197-218). The use of these sulphur compounds as fumigants in the treatment of stored foodstuffs has never been generally accepted. Patent application FR-A-2 779 615 filed in 1997 discloses a particular technique for the application of such treatments: the circulation of gas in a loop in a sealed silo by means of a pump. Indeed, it is essential for a fumigant for the treatment of stored foodstuffs to diffuse the treatment rapidly in the gaseous form in the mass to be treated. However, it has been demonstrated by the applicant that these sulphur-containing products spontaneously diffuse too slowly in a mass of grains, causing large differences in the gas concentration inside this mass and therefore an inefficiency in the treatment. The solution proposed in the abovementioned patent application, consisting in carrying the active gas in a stream of air or of air enriched with CO2, is an expensive technique which is not available on the majority of existing installations and which is difficult to apply because of the lack of leaktightness in the majority of installations for the storage of foodstuffs.